Modulation-enabled healable and stretchable shape-memory polymer composites for digital light processing 4D printing

Abstract

4D printing provides viable pathways for 3D-printed objects that require morphological, time-dependent adaptations. Among various 4D printing materials, shape-memory polymers (SMPs) are one of the most extensively utilized morphing materials. However, most existing SMPs in 4D printing systems suffer from irreparability and low stretchability due to abundant covalently cross-linked networks. Also, their shape-programming steps typically involve stringent temperature requirements (≥90 ºC) and lack strategies for remote controllability, significantly restricting their applicability. Herein, we report a novel thermoplastic polymer system with self-healing and highly stretchable shape-memory capabilities for digital light processing (DLP)-based 4D printing. This system was attained through the integration of two distinct compositions: a polymer-based framework that acts as the reinforcing phase; and an elastic lubricant featuring hydrogen bonds that facilitates self-healing, high stretchability, and enhanced shape recovery. Additionally, light-responsive capabilities were shown to be effectively achieved by introducing a novel cross-linker functionalized with biomass lignin. The rationally selected safer set of ingredients ensures that our printed shape-memory polymer composites (SMPCs) are biocompatible. We further demonstrate their potential applications in aerospace and healthcare. This work provides a foundation for the design and facilitation of intelligent materials, showcasing excellent properties across multiple fields.